Screw compressor



Dec. 11, 195] c J MONTELIUS 2,578,196

SCREW COMPRESSOR Filed Nov. 30, 1946 3 Sheets-Sheet 1 IN! 'E.\' TOR.

(arl Oscar Josef [10111611116 Dec. 11, 1951 c. o. J. MONTELIUS 2,578,196

SSSSS SSSSSSSS OR I I 7 INVENTOR.

19 32. 15 arl Oscar Joaef Monielius Patented Dec. 11, 1951 scunw oomrlmssoa Earl Gscar Josef Montelius, Stockholm, Sweden,

assignor to Alt-:tieholaget Hmo-Industri, Stoolshohn, Sweden, or company or Sweden Application November 3d, 1943, Serial No, 713,343

d llllas, (i, 230-ll4ii-l) This invention relates to screw compressors oi the type having a plurality of intermeshing rotors enclosed in a housing and has particular reference to the securing of proper discharge from such a compressor.

in screw compressors the rotors are placed in a housing having inlet and outlet openings, the inside of the housing having intersectin bores to fit the outsldes of the rotors. Contrary to the practice in the case of pumps for incompressible liquids, an end wall of the housing is located against the pressure (outlet) end or the rotors, to compress the volume enclosed in the individual grooves lociore the rotors have reached the rotary position where these grooves open to the outlet. Further: it is a common practice to sup port the rotors by hearings avoid contact ha tween the rotors and the housing and to couple them by gear wheels to avoid direct friction between the screw threads of the intermeshing rotors. The shape of the screw threads is such that one of the cooperating rotors (the male" rotor) is arranged with convex flange sides, the other (the female rotor) with concave flange sides (as in Patents 1,708,891 or 2,321,696) to avoid unnecessary leakage in all positions.

The outlet opening in the housing, which should be placed and dimensioned so that it permlts a discharge at the right moment, when the compression in the grooves has reached a desired value, has been either placed sideways along the circumference of the rotors or in the pressure end wall or both ways. None of these arrangements, however, is satisfactory.

If the outlet is placed only sideways, it will allow the main part of the compressed gas to escape, but a small volume will be entrapped between the rotor threads and the end wall.

If, on the other hand, the outlet is placed in the end wall or so that it opens both sideways and to the end wall, this entrapped volume can escape, but then a direct passage from the out let or high pressure side to the low pressure side cannot be avoided in certain positions of the rotors.

In the present invention a free outlet is arranged only sideways, the end of one oi the cooperating rotors being closed by a valve plate fixed on this rotor with a. necessary clearance with the end wall. In this valve plate passages from each rotor groove are made adjacent to one side of the rotor threads and cooperate with a. channel in the end wall, which is connected to the outlet but covered by the valve plate. This channel is placed in such position that it drains the trapped volume to the outlet.

In the drawings,

Fig. 1 shows a length-wise seotion of a coinpressor according to the invention;

Fig. 2 is an and side viewer the same compressor;

Figs. i and 5 show a section alon the line Jimill in Fig. 1 illustrating the rotors in three diflerent positions; and

Fig. 6 corresponds to Fig. 3, but involves avalve plate fixed upon the male screw instead of the female screw.

lln l. and Fig. 2 the housing is divided in two parts i and 22 secured together by four bolts and nuts indicated at The ends of. the housing are closed. by two end covers 6 and 5. In the housing two rotors and i are supported at one end hy roller hearings t; and at the other end by hall hearings The rotor has a driving shaft it) to be driven by a motor. At the opposite end gear "vheels El and G2 are fixed upon the rotor shafts, coupling them together. The inside of the two parts i and 22 of the housing is machined in the shape of two intersecting bores fitting the cylindrical outside surfaces of the rotors and the end walls of these bores are machined to planes fitting the plane ends of the rotors. The rotors are machined to screw shapes or opposite pitch, the rotor 6 being a male screw with convex flanges, the rotor l a female screw with concave flanges. The housing is further provided with an inlet openin it at one side and an outlet opening it at the other side. In Fig. l the inlet it and the outlet M are indicated by dotted lines.

At the outlet end of the rotor l a plate is fixed upon the rotor. This end plate is and the rotors are further illustrated in Figs. 3, 4 and 5. The female screw TI is designed with four threads l6 and is rotated in the direction indicated by the arrow. Along the back side ll of each thread anoblong opening I8 is cut in the end plate. Along the end wall of the inside of the housing facing the plate a groove or channel I9 is machined formin a. conduit for the compressed gas to the outlet It.

In the operation of the machine the rotor 6 is rotated, driven by the shaft l0 and driving the rotor I by the gear wheels II and Hi. The rotor threads have such a shape that the grooves on both rotors are closed by the threads of the other rotor and by the housing, making a set of closures, which are constantly moving lengthwise from the suction end wall 20 in Fig. 1 to the pressure and wall 2|. These closures are filled by a fluid through the inlet [3 which is compressed during the rotation. In a. certain 3 position the tops of the threads by their rota.- tion reach a position where the closures open to the outlet opening ll. Durin the following rotation the main part of the volume in the 010- sure is expelled through this outlet H.

In Figures 3-5 the rotor ends close to the pressure end wall 2| are illustrated. The rotor groove 22 in the rotor 6 in Fig. 1 is marked by the same number in Fig. 3. This rotor groove opens to groove 23 in the rotor 1 in both Figs. 1 and 3. They form together a closure, which is in this position open to the outlet [4. The following grooves 24 in rotor 6 and 25 in rotor 1 form together another closure with a greater volume. This latter closure is open neither to the inlet, nor to the outlet and its volume will be compressed. The main part of the gas in these rotor closures, for instance 22 and 23, will escape to the outlet [4, but in each case a small part of the gas is trapped in the space 26, when the front face 21 of a flange of the male rotor 6 closes a groove 28 of the female rotor. This trapped volume escapes through the valve opening l8 to the channel I9 in the housing, which opens to the outlet I4.

During the following rotation the position shown in Fig. 4 is reached. The opening I8 is still open to the channel 19, but when the rotors have reached the position in Fig. 5, the opening I8 is shut off from the channel Hi.

It is necessary that the opening I8 is placed only along the back side of the female rotor threads. Otherwise a passage would be created from the outlet I4 and the groove [9 to the back side 29, Fig. 4 and Fig. 5, of the male thread. The crescent-shaped area between the back side 29 and the female front side 30 indicates the beginning of a canal along the rotor threads, widening to the suction side or inlet. If therefore the opening I8 would be too wide and open to this crescent-shaped passage, the compressed fluid would escape this way causing a considerable loss and noise.

The valve plate can be fixed upon the male rotor instead of the female one. In Fig. 6 the arrangement of the passages is illustrated in a position corresponding to that of Fig. 3. The arrangement differs only from that previously described in that the openings 3| in Fig. 6 are placed along the front side 32 of the male screw instead of along the back side of the female screw as was previously described.

rotor cooperate with two or more female rotors.

Each of these female rotors should then be provided with a valve plate according to the invention. It is also possible, when a plurality of female rotors are used, to arrange a single valve plate upon the male rotor.

Having now particularly described the nature of my invention and the manner of its operation what I claim is:

l. A screw compressor including a housing, intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and a valve plate carried by one of said rotors at the compression end thereof, said valve plate having a plane face engaging fiatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the part of the end wall which is within the circumferences of both screws and said outlet opening, and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening.

2. A screw compressor including a housing, intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and a valve plate carried by the male rotor at the compression end thereof, said valve plate having a plane face engaging fiatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the part of the end wallwhich is within the circumferences of both screws and said outlet opening. and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening.

3. A screw compressor including a housing. intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and a valve plate carried by the female rotor at the compression end thereof, said valve plate having a plane face engaging fiatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the part of the end wall which is within the circumferences of both screws and said outlet opening, and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening.

4. A screw compressor including a housing, intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and a valve plate carried by one of said rotors at the compression end thereof, said valve plate having a plane face engaging fiatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the part of the end wall which is within the circumferences of both screws and said outlet opening, and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening, each opening in said valve plate being adjacent to a side of a thread of the rotor which carries the plate.

5. A screw compressor including a housing. intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and

a valve plate carried by the male rotor at the compression end thereof, said valve plate having a plane face engaging fiatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the part of the end wall which is within the circumferences of both screws and said outlet opening, and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening, each opening in said valve plate being adjacent to the leading side of a thread of said male rotor.

6. A screw compressor including a housing, intermeshing male and female screw rotors within the housing, said housing having inlet and outlet openings, the outlet opening being laterally related to said screws to provide escape for elastic fluid compressed within the rotor grooves, and a valve plate carried by the female rotor at the compression end thereof, said valve plate having a plane face engaging flatwise a plane surface on an end wall of the housing, said end wall of the housing having a passage therein providing communication between the region inside the 6 part of the end wall which is within the circumferences of both screws and said outlet opening, and said plate being provided with openings furnishing communication between the rotor grooves and said passage for the escape of elastic fluid entrapped in said grooves after closure of the grooves following their communication with the outlet opening, each opening'in said valve plate being adjacent to the trailing side of a thread of said female rotor.

CARL OSCAR JOSEF MONTELIUS.-

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 165,805 Disston July 20, 1875 1,409,868 Kien Mar. 14, 1922 1,708,891 Montelius Apr. 9, 1929 1,994,397 Loveridge et al. Mar. 12, 1935 2,130,054 Whitfield Sept. 13, 1938 2,236,980 Ungar Apr. 1, 1941 2,287,716 Whitfield June 23, 1942 2,321,696 Montelius June 15, 1943 2,460,310 Rathman Feb. 1, 1949 

